The present invention relates to a device for the measurement of the diameter of cylinders, and more particularly in a machine tool such as a roll grinding machine Such a device is disclosed in the French patent 1,427,548, wherein a rotational pickup is provided that is coupled with a contact wheel, which is adapted to run on the surface of the cylinder. This contact wheel is bearinged on a rotary, rod-like carrier, which has a pulse device that produces one pulse for each rotation of the rod, the rod consisting of a magnet coupled with the rod, a stationary magnet, and transmission and indicating devices. In this case, practically only complete rotations of the rod are detected and on the basis of the number of pulses, which occur during these detected revolutions at the rotational pickup, the diameter (preferably the internal one) of the cylinder, which remains stationary, is measured. This method of measurement is naturally relatively inaccurate and has a slow response. Furthermore it has the substantial disadvantage that a very large number of rotations of the contact wheel are used in each measurement operation for the calculation of the cylinder diameter, any error in the measured or known diameter of the friction wheel being multiplied.
In this respect it is moreover a question of a machining device resembling a drilling machine and apparently intended for the production of relatively small holes using a simple bar-like cutting tool.
One object of the present invention is to provide a measurement device that has an extremely high accuracy of at least .+-. 0.002 mm and, preferably of .+-.0.001 mm, in the case of cylinder diameters of between 200 and 3000 mm.